The present invention relates to an electronic circuit and a method with such a circuit for the monitoring of the driving force of a drive mechanism, preferably an electromotive drive mechanism.
To monitor the driving load of a drive mechanism, electronic circuits are used in driving technology which generate an error signal as soon as the operating state of the drive mechanism deviates from a defined value. In the case of automatically driven doors, for example, such a monitoring circuit serves above all to prevent persons from being injured when they unforeseeably enter the closing area during the closing of the door. A monitoring circuit of this type can generally also protect the drive mechanism against overload and so against destruction.
The monitoring circuits which are usually employed are based on the fact that a measured value characterizing the driving load and a defined set point are supplied to a comparator unit. This generates an error signal as soon as the measured value exceeds the set value with the set value then representing the maximally permissible driving load in this case. If the monitoring circuit is realized within the framework of a microprocessor control system, then the set value is generally available in digital form, for example as a value stored in a memory. The detection of the measured value is usually performed with an analog-digital converter so that the measured values can be evaluated in the microprocessor control system. However, such an arrangement has the disadvantage that high component costs are incurred due to the use of an analog-digital converter. In addition, an analog-digital converter for the detection of measured values requires a complicated filter wiring to avoid aliasing effects.